Immunology

What happens to the B cells in the humoral response

1. Foreign antigens are recognized and taken up by B cells; they are processed and then presented on the surface of the B cell 2. Activated T helper cells attach to the processed antigens on the surface of the B cell and activate the B cells 3. The activated B cells can then divide by mitosis to give a clone of B cells with the same receptor (clonal selection). The B cells can then differentiate into either plasma cells or B memory cells 4. The cloned plasma cells produce antibodies that are complementary in shape to the foreign antibody. These antibodies can bind to the foreign antigen and destroy the pathogen (neutralise) 5. The B memory cells continue to circulate in the bloodstream after the infection has been tackled (and the plasma cells and antibodies have disappeared) These can respond to future infection by the same pathogen, by rapidly dividing and producing many plasma cells and lots of antibodies quickly

What happens during cell mediated immunity when T lymphocytes respond to an infection

1. Pathogens invade body cells or pathogens are phagocytosed. They now become digestion products 2. These antigen presenting cells present the foreign antigen (digestion products) on the surface of the cell 3. A receptor on the surface of a specific T helper cell fits exactly / complementarily to the foreign antigen. An antigen- receptor complex is formed 4. This binding activates the T cells to divide by mitosis. This is called clonal selection or clonal expansion 5. The cloned T cells can differentiate into different types of T cell which have specific roles in the immune response

How maby polypeptide chains make up an antibody?

4- 2 heavy chains and 2 light chains

How is the stomach seen as the primary defence

Acidic conditions here denature the pathogen's enzymes

What is produced during the primary immune response

After being exposed to antigen both B + T lymphocytes produce memory cells. They remain in the body for a long time. Memory T lymphocytes remember the specific antigen and recognise it 2nd time around. Memory B lymphocytes record the specific antibodies needed to bind to the antigen and the person is now immune

How is the throat primary defence

Airways and digestive tract are very open to infection. Mucus membranes offer protection. Mucus is secreted by goblet cells. Pathogens trapped in the mucus are moved in a coordinated fashion by cilia which waft the mucus to the top of the trachea where it can enter the oesophagus

What is the significance of the hinge region

Allows flexibility so that they are able to attach onto antigens

What is specificity

An antibody is specific to a particular antigen because of the shape of the variable region. Each type of antibody has a differently shaped variable region

What is the difference between an epidemic and a pandemic

An epidemic is specific to one city, region or country. A pandemic covers a much wider geographical area- often worldwide and infects many more people. A pandemic goes further than national borders

What happens during neutralizing toxins

Antibodies can bind to the toxins produced by pathogens. This prevents the toxins from affecting human cells so the toxins are neutralised (inactivated). The toxin antibody complexes are also phagocytosed

What blood cells produced antibodies

B cells

Why do we need to find new drugs

Development of antibiotic resistance New diseases Some diseases do not have effective treatment Commercial reasons

What are aggulutinating pathogens

Each antibody has two binding sites so an antibody can bind to two pathogens at the same time- the pathogens become clumped together. Phagocytes then bind to the antibodies and phagocytose a lot of pathogens all at once

Compare active immunity and passive

Exposure to the antigen/ no exposure to the antigen It takes a while for protection to develop/ Protection is immediate Protection is long term/ Protection is short term Memory cells are produced/ Memory cells aren't produced

Describe what happens during identification

Fist signalling done by the pathogen Pathogen carries antigens on the cell surface membrane. Acts as markers and are detected by body cells

Describe the four features of the antibody structure

Four polypeptide chains held together by disulfide bridges A constant region which is the same in all antibodies. This enables the antibody to attach to phagocytic cells and helps in the process of phagocytosis A variable region which has a specific shape and differs from one type of antibody to attach only to the correct antigen. The shape of the variable region is complementary to that shape of antigen and can bind to that antigen. Hinge regions which allow a further degree of flexibility. These allow the branches of the Y shaped molecules to move further apart in order to allow attachment to more than one antigen

What is the immune response 2

If a pathogen or parasite gets past primary defences the immune system will respond An immune response is the body's reaction to a foreign antigen

How are scars seen as primary defence

If damaged clotting can occur. Soluble, globular fibrinogen is converted to the insoluble fibrous protein fibrin. This forms a mesh of ... at the site of the wound that traps platelets forming a scab

What is the secondary immune response

If the same pathogen enters again- immune system produce quicker, stronger immune response. Memory B cells divide into plasma cells that produce the right antibody to the antigen. Memory T cells divide into correct T cells to kill the cell carrying the antigen. Removes pathogen before you get any symptoms

How does the immune system respond to a vaccine?

Immune system treats the antigenic material as a real disease. The immune system manufactures antibodies and memory cells. The memory cells provide the long term immunity.

What is the role of macrophages

Infected cells release chemicals such as histamines which attracts neutrophils Histamine also makes capillaries more leaky Therefore fluid leaves the capillaries at the areas of infection This causes swelling and redness and more fluid passes into the lymphatic system , leading pathogen to macrophages waiting in the lymph nodes Macrophages then play a part in activating lymphocytes

Why is influenza such a threat

It affects the respiratory system. People over 65 and those with other respiratory tract conditions are particularly at risk Occasionally a new strain of flu virus arises that is particularly virulent

Why are some vaccines taken orally as opposed to injections

It could be broken down by enzymes in the gut or the molecules of the vaccine may be too large to be absorbed into the blood

What is a vaccination

It is deliberate exposure to antigenic material which activates the immune system to make and immune response and provide immunity

What is the immune response 1

It is specific response to a pathogen which involves the action of lymphocytes and the production of antibodies

What are the examples of communcation using cytokines

Macrophages release monokines that attract neutrophils (by chemotaxis- the movement of cells towards a particular chemical) Macrophages release monokines that can stimulate B cells to differentiate and release antibodies T cells, B cells and macrophages release interleukins which stimulate proliferation and differentiation of B and T cells Many cells can release interferon which can inhibit virus replication and stimulate the activity of T killer cells

Describe macrophages

Made in the bone marrow Travel as monocytes when they travel in the blood Settle in organs (called Kupffer cells in liver) especially lymph nodes where they become macrophages Important role in specific response to pathogens Help break up invading pathogen and then present some of the molecules on their surface- antigen presenting cells relatively longer life

4 facts about T lymphocytes

Made in the bone marrow but mature in the thymus gland Involved in cell- mediated immunity (antigens must be presented on the cell surface) Responds to foreign material inside body cells (foreign antigens presented) and body cells modified by viruses or cancer and transplanted cells Have T cell cell receptors and do not secrete antibodies

What is the second line of defence

Many trapped pathogens are not killed by the conditions in the body. These pathogens must be killed before they reproduce and cause the symptoms of disease. This is the job of numerous and non-specific pathogens There are two types: neutrophils and macrophages

5 facts about the B lymphocyte

Mature in the bone marrow Involved in the humoral response (antibodies) Responds to foreign antigens outside body cells and bacteria and viruses Each B cell has around 10^5 membrane bound antibody molecules on its surface Every human has around 10^8 different types of B cell making antibodies with each only responding to one specific antigen

Can immunity be maintained forever

Memory B and T lymphocytes only have a limited life span. Once all the memory B and T lymphocytes have died the person may be susceptible to attack by the pathogen again. Immunity can be maintained by being continually exposed to the pathogen so you continue to make more and more memory B and T lymphocytes

How are the eyes and mouth the primary defence

Moist surfaces which are bathed in fluid that has bactericidal action. Lysozyme is found in saliva and tears

What are antigens

Molecules that stimulate an immune response

Describe neutrophils

Most common- 60% of white blood cells multi-lobed nucleus Made in the bone marrow Travel in blood and squeeze into tissue fluid Found on the surface of tissue in lungs Short lived and large numbers

Define natural and artificial immunity

Natural- gained in the normal course of living processes. It may be gained as a result of an infection that stimulates an immune response Artificial- gained by deliberate exposure to antibodies or antigens

Give an example of passive natural and artifical immunity

Natural: Antibodies provided via placenta or breast milk. Makes the baby immune to disease similar to the disease in the mother. It is useful in the first year when the baby's immune system is developing Artificial: Immunity provided by infection of antibodies made by another individual

Give an example of active natural and artifical immunity

Natural: Immunity provided by antibodies made in the immune system as a result of infection. A person suffers from the disease once and is then immune Artificial: Immunity provided by antibodies in the immune system as a result of vaccination. A person is infected with a weakened, dead/similar pathogen or with antigens + activates the immune system

Once an influenza vaccine is developed what happens

New vaccines are developed and one is chosen every year that is the most effective against the recently circulating viruses. Government and health authorities then implement a programme of vaccination using the most suitable vaccine.

What happens for a non specific response

Non-specific= This response is immediate and is the same for all pathogens Physical barrier= eg. skin stops pathogens entering the body Phagocytosis= inflammatory response where the pathogens are digested - mmune response

Compare Primary and secondary response

Pathogen: enters for 1st time, Enters 2nd time Speed of response: Slow, Fast Cells activated: B and T lymphocytes, Memory cells Symptoms: Yes, No Similarities: Both are triggered by the invasion of the body by a pathogen, both ultimately get rid of the pathogen and both involve the production of antibodies

What happens during phagocytosis

Phagocytes circulate in the blood and can move into tissues to engulf non-self antigens. a) A pathogen releases chemoattractants which cause the phagocytes to move towards the pathogen b) Phagocytes also have membrane bound receptors which attach to antibodies already attached to antigens on pathogens 2) Phagocytes attach themselves to the surface of the pathogen 3) The phagocyte engulfs the pathogen into a membrane bound vesicle called a phagosome 4) Lysosomes (vesicles containing digestive enzymes called lysins) fuses with the phagosome 5) The enzymes break down the pathogen and the digestion products are absorbed into the cytoplasm of the phagocyte. Neutrophils are short-lived and will die soon after digesting a few pathogens. Pus may form

Why is biodiversity important when finding new drugs

Possible sources of drugs need to be protected by maintaining the biodiversity on earth. If we dont protect then some species could die out before we are able to study them. Even organisms that have already been studied are useful as new techniques are developed for identifying purifying and testing compounds

Why is developing a vaccine for influenza so difficult

Proteins on the surface of the influenza virus act as antigens triggering the immune system. These antigens can change regularly forming new strains of the virus. Every year there are different strains of the influenza virus circulating in the population so a different vaccine has to be made

What are self antigens and foreign antigens

Self antigens- help the body cells to recognize each other

How is the penis the primary defence

Semen contains a bactericide called spermine

What is the significance of the variable region

Specific and different for each antibody- so the antibody attaches onto a specific antigen

How does the immune response use cell signalling

Specific response to detection of pathogens. Communication achieved through release of hormone like chemicals= cytokines. Detect signals from the target cell= cell surface receptor B and T cells = receptors complementary in shape to foreign antigens. Antigen= isolated protein/ attached to pathogen. Antigen detected and lymphocytes are activated

What are the different types of T cells and what do they do

T memory cells: (long lasting immunity) circulate in the blood and tissue fluid ready to respond to a future infection by the same pathogen T helper cells: release cytokines to stimulate B cells to divide T helper cells: stimulate phagocytosis T killer cells: kills infected cells by making holes in the cell membrane using a molecule called perforin

Describe antigen presentation

Taken a step further by the macrophages in the lymph nodes Macrophages act like phagocytes to engulf and digest the pathogen- do not fully digest it. Separate out antigens and incorporate them into a cell surface molecule. This is exposed on the surface of the macrophage which becomes known as an antigen-presenting cell. Its function is to find the lymphocytes that can neutralise that particular antigen

What is the significance of the constant region

The same for every antibody- allows them to interact with phagocytic cells

What is the most important primary defence

The skin as it covers most of the body. The outer layer, epidermis consists of cells called keratinocytes. These are produced at the base of the epidermis and as they move to the surface they dry out and and the cytoplasm is replaced by the protein keratin- keratinisation. As they move towards the surface, they die and are sloughed off. The keratinised layer of dead cells acts as an effective barrier to pathogens

In cell communication for the immune response what do the cytokines do

These are chemical signals released by the cell. They act as instructions to their target cells. Act over short distances at low conc. Act by binding to specific membrane-bound receptors on the target cell. Causes the release of second messengers

What is the primary defence

These attempt to prevent pathogens from entering the body

What is the structure of an antibody

They are Y shaped and have two distinct regions

What are antibodies made from

They are made from globular protein- immunoglobulin

Where are antigens found and what are they made of

They are made of glycoproteins- carbohydrates and proteins

Describe antibodies

They are produced by the lymphocytes in the immune system. They are released in the response to an infection. They are large proteins and have a specific shape that is complementary to that of a particular antigen. Therefore antibodies are specific to particular antigens. Our immune system must manufacture one type of antibody for every antigen that is detected.

What are antibodies

They are protein molecules that can identify and neutralize antigens

What are the two affects of parts of the pathogen being attached to the plasma membrane

They can act as distress signal and can be detected by cells from the immune system They also acts as markers to indicate that the host cell is infected- T killer cells can recognize that the cell is infected and must be destroyed

Why are booster vaccines used

They ensure that memory cells are still produced

What happens for a specific response

This response is slower and is specific to each individual pathogen Cell mediated response= T lymphocytes white blood cells which respond to pathogens using cells Humoral response= B lymphocytes white blood cells which response to pathogens using antibodies

What is ring vaccination

Vaccinating all the people in the immediate vicinity of the new case. May mean vaccinating the people in surrounding houses or even the whole village or twon Used to control the spread of livestock disease

When are antibodies produced

When a bacterium/pathogen/foreign bodies enter the bloodstream

Describe sending distress signals

When a body cell is infected it is damaged Lysosomes try to fight invaders but as a result no. of pathogen cells are damaged. Part of the pathogen often end up attached to the host plasma membrane.

What is the primary immune response

When an antigen enters the body for the first time it activates the immune system. It is slow as there aren't many B lymphocytes that can make the antibody needed to bind to it. Eventually the body will produce enough of the right antibody to overcome the infection. But the infected person will show symptoms of the disease

What happens to prevent the pathogen binding to human cells

When antibodies bind to the antigens on pathogens they may block the cell surface receptors that the pathogens need to bind to the host cells. This means the pathogen can't attach to or infect the host cells

What material is found in the vaccination

Whole, live microorganisms- not as harmful as those ones who cause the real disease Harmless/attenuated version of the pathogenic organism A dead pathogen A preparation of the antigens to form a pathogen

Fill in the gaps B cells with the appropriate ....... to ........... bind to ........................... , are not produced in response to a pathogen B cells are preset from ...... they simply. ........ in response to the ........... One pathogen will consist of many ........... and you only need one ................. to produce a humoral response

antibody complementarily antigens of a pathogen birth multiply pathogen different antigens complementary B cell receptor

Draw each of the stages of phagocytosis

...

Draw each stage of the humoral response for B cells

...

How many antibodies are there for each antigen

1 antigen per antibody

How do we find new drugs

By accident eg. Fleming anaesthetics- opium/poppies observation of wildlife eg. elephants eating clay for dietary toxins traditional medicine eg. chinese medicine and herbs research eg. pharmacologist

What is cell signlling

Communication between cells that allow effective coordination of a response

How is the vagina primary defence

Conditions here are relatively acidic due to non-pathogenic bacteria secreting lactic acid. If the women take antibiotics, pH rises and infections can occur. A common one is Candida